GB2036533A

GB2036533A - Intermediate moisture food products

Info

Publication number: GB2036533A
Application number: GB7846619A
Authority: GB
Original assignee: Societe des Produits Nestle SA; Nestle SA
Current assignee: Societe des Produits Nestle SA; Nestle SA
Priority date: 1978-11-30
Filing date: 1978-11-30
Publication date: 1980-07-02
Also published as: DE2965538D1; MX6279E; EP0012255A1; JPS5577881A; AU524176B2; ZA796322B; ATE3497T1; CA1136477A; NZ192187A; EP0012255B1; AU5323279A; ES486435A1; JPS5714150B2

Abstract

Pasteurised intermediate moisture food products have a water activity of from 0.86 to 0.91 and a pH of from 4.5 to 5.5, the food products having been pasteurised in containers which have been hermetically sealed before, during or immediately after pasteurisation. The food products may be stored for extended periods without refrigeration and without spoilage by microbial or mould generation. The preparation of intermediate moisture vegetables, vegetable cakes, tortellini, pancakes and waffles are particularly described.

Description

SPECIFICATION Intermediate moisture food products This invention relates to intermediate moisture food products. Intermediate moisture food products have been developed in recent years as storable food products which do not require special storage conditions such as refrigeration, canning and the like, but which substantially retain the characteristics of the original food product. Such products are sometimes known as "semi-moist" foods as they have a moisture content between that of a food having its usual moisture content and a dried food. In general such foods have a moisture content greaterthan 10% and less than 50% by weight. The microbiological stability of intermediate moisture food products characteristically is provided partly or wholly by reducing the amount of water available for vital processes incident to microbial growth and spore germination and outgrowth. As the amount of water available for such spoilage processes bears a close relationship to the vapour pressure of the water in the product (since the vapour pressure is a function of unbound water), it has become the practice in the art to characterise intermediate moisture food products by their water activity, Aw, which is defined by the relationship Aw = P/Po (wherein P is the vapour pressure of water in the food, and Po is the vapour pressure of pure water at the same temperature).In general, most microorganisms can grow when the water activity is in the range 0.97 to 1.00, but a large proportion of common bacteria will not grow if the water activity is below 0.91. Yeasts and moulds generally require the water activity to be below 0.88 and 0.80 respectively to prevent growth. Similarly, staphylococcus organisms, halophilic bacteria, xerophilic moulds and osmophilic yeasts generally will not grow if the water activity is below 0.85, 0.75, 0.65 and 0.60 respectively. Intermediate moisture food products are at present generally prepared with water activities in the range 0.60 to 0.85. However, it is desirable to ensure thatthe water activity is as high as possible, while ensuring the avoidance of risk of spoilage or growth of pathogenic bacteria, in order to preserve more natural organoleptic properties and textures. Such known products often incorporate antimicrobial agents when the water activity is in the upper end of the above range, in order additionally to control the growth of undesired organisms in the products but it would be preferable if such additives could be avoided. Water activities below 0.91 are sufficiently low to inhibitthe growth of all heat resistant bacteria but certain heat sensitive bacteria, yeasts and moulds are still able to to proliferate at relatively high water activities below 0.91. Staphylococcus aureus is of particular significance in this respect. It has therefore sometimes been the practice to pasteurise intermediate moisture food products priorto packaging in order to kill any heat sensitive organisms. However, the pasteurisation techniques which have been employed either are not fully effective in killing all the microorganisms as these have an increased heat resistance at the water activity levels which have been used in known intermediate moisture food products or are so severe that poor quality products result.In addition, pasteurisation has hitherto been effected priorto packaging the food products and this has given rise to a risk of re-contamination with undesirable microorganisms in subsequent packaging procedures. It is therefore an object of the present invention to provide intermediate moisture food products having a relatively high water activity, but with adequate resistance to spoilage and production of toxic products by growth of microorganisms. We have found that the above objects may be achieved by combining a relatively high water activity with controlled acidity and by pasteurisation of the food product in a container which is hermetically sealed before, during or immediately after pasteurisation. Thus, according to one aspect of the present invention there is provided a pasteurised, intermediate moisture food product having a water activity of from 0.86 to 0.91 and a pH of from 4.5 to 5.5, said food product having been pasteurised in containers which have been hermetically sealed before, during or immediately after pasteurisation. According to a further aspect of the invention there is provided a process for the preparation of intermediate moisture food products which comprises pasteurising a food product having a water activity of from 0.86 to 0.91 and a pH of from 4.5 to 5.5, within a container and hermetically sealing the container before, during or immediately after pasteurisation. The desired level of water activity of the intermediate moisture food products according to the invention may be conveniently achieved by two methods. The first of these methods comprises physically reducing the water content by drying the food product itself or some or all of the raw ingredients thereof. Of course it is also possible to use a combination of these drying methods, whereby the raw ingredients are dried as well as drying of the food product itself. The second method of reducing the water activity of the food product according to the invention is to incorporate at least one edible humectant, which binds a proportion of water to such an extent that it is unavailable for microbial growth. Such humectants include water-soluble sugars, salts, polyhydric alcohols and acids.From economic considerations and having regard to the flavouring and ease of use characteristics of such humectants, it is preferred to use glycerol, sucrose, dextrose, propylene glycol, sodium chloride and/or sorbitol, for this purpose. In general, however, it is preferred to use a combination of both of the above techniques, that is to dry some or all of the ingredients or the food product itself, and to incorporate a humectant or mixture of humectants. The food products according to the invention have a pH in the range 4.5 to 5.5 and this may be achieved by incorporating a suitable amount of, for example, an acceptable food acid such as acetic, citric, lactic, malic ortartaric acid, into the food product. If the use of a free acid in the food product would affect its properties by reaction with other ingredients, such as for example in farinaceous products containing raising agents, it is preferred to incorporate an acidulating agent which will avoid such reaction. For example, we have found that glucono-8-lactone or sodium acid pyrophosphate may be used as acidulants in batter-derived food products containing raising agents. The food products according to the invention are packaged with hermetically sealable containers and are pasteurised therein. This pasteurisation may be effected by hot filling the containers and/or by subsequently heating of the filled containers, for example by steam or hot water, by microwave heating, or by a combination thereof. It should be noted that pasteurisation will not necessarily kill all undesired organisms in the food products according to the invention, but the growth of any microorganisms surviving pasteurisation will be inhibited by the combination of low water activity and low acidity in the food products. In general, pasteurisation will be sufficientto kill all non-sporing microorganisms and many heat-sensitive sporing microorganisms, such as yeasts and moulds.Thus, the pasteurisation process will be sufficient to kill those microorganisms which may be capable of multiplication at the levels of water activity and pH present in the food products according to the invention. The use of relatively high water activities in the food products according to the invention may give rise to improved properties compared with intermediate moisture food products having lower water activities. In particular, the higher water activity requires the use of smaller quantities of humectants for preservation with a consequent improvement in flavour or organoleptic characteristics. In addition the food products are "moister" to the palate. The increased moistness also improves the reheating properties of the food products according to the invention when these are being prepared for consumption, as heat transference is more efficient. This characteristic is of particular importance when the food products of the invention are in the form of the so-called "boil-in-the-container" type. A further advantage of the use of relatively high water activities of the food products according to the invention is thatthe pasteurisation efficiency is improved as a result of the better heattransfer properties. We have found thatthe use of relatively high water activities in conjunction with controlled addification in food products according to the invention renders microorganisms more susceptible to the damaging effects of,mild heattreatment, such as pasteurisation, than is the case in hitherto known intermediate moisture food products. The intermediate moisture food products according to the present invention do not require the presence of antimycotic agents. The avoidance of the use of such agents is especially desirable in view of the restriction on the use of such products in some areas and also the sales resistance which may be encountered when the presence of such agents is indicated on product labels. The in-pack pasteurisation process used in the preparation of intermediate moisture food products according to the invention prevents any recontamination of the food products which is possible in the hitherto used procedures of pasteurisation priorto packaging. The present invention is of particular applicability to food products of the pancake or waffle type. Thus in certain embodiments of the invention there are provided fully cooked pancakes and waffles in hermetically sealed containers such that they may be readily reheated prior to consumption. Such pancakes and waffles may be stored for extended periods without refrigeration and do not significantly deteriorate during such periods. When reheated these pancakes and waffles are of comparable flavour, aroma, appearance and texture compared to freshly prepared pancakes and waffles. Pancakes and waffles according to the invention may be produced by cooking batters containing such levels of humectant and/or such levels of water that the resultant water activity of the cooked products is in the range 0.86 to 0.91. For example we have found that batters containing from 0 to 18%, preferably about 8%, of glycerol together with from 15 to 5%, preferably about 9%, of dextrose monohydrate, and having a moisture content of from 35 to 55%, preferably about 45%, will give fully cooked pancakes or waffles having a glycerol content of from 0 to 20%, a dextrose content of from 20 to 5% and a moisture content of from 32 to 42%. When pancakes or waffles are prepared using batters containing the above mentioned preferred levels of glycerol, dextrose and moisture, the fully cooked products generally contain about 7.0% glycerol, 10% dextrose and 37% moisture. The pancakes and waffles according to the invention may be prepared from batters which incorporate the usual components such as, for example, edible oils or shortenings such as for example, hydrogenated and non-hydrogenated forms of groundnut oil, coconut oil, cottonseed oil, sunflower oil, palm kernal oil and mixtures thereof; eggs; salt; flour; milk; whey; and raising or leavening agents. As indicated above the preferred acidulating agents for batters containing raising agents such as sodium bicarbonate, are glucono-8-lactone or sodium acid pyrophosphate. Pancakes and waffles according to the invention may be conventionally cooked on a hot plate or griddle and may be then packed into hermetically sealable containers and pasteurised. The method of the invention may conveniently be applied to vegetables and vegetable based products. Thus, for example, onions may be sliced, steeped in humectant, pressed to remove excess liquor and air-dried to give an intermediate moisture product of about 25% of the weight of the original onions. This product may then be mixed with further humectant, filled into plastic pouches and pasteurised. We have also found that the present invention is applicable to pasta products such as, for example, tortellini. The following Examples serve to illustrate the production of food products according to the invention:- Example 1: Ready-to-eatPancakes

The flour, sodium bicarbonate, acidulant, whey powder, salt, dextrose and sugar were mixed together. The egg was added with a little water and mixed in thoroughly. The oil, glycerol and remaining water were then added sequentially and the mixture was mixed to form a smooth homogenous batter. The batter was then transferred to pancake moulds placed on a greased hotplate. The pancakes were cooked on each side. The Aw of the batter was approximately 0.93 at 25[deg]C and its pH was 5.5. The Aw of the cooked pancake product was 0.87 at 25[deg]C and its pH was 5.4. The pancakes were transferred to thermoformed trays formed from a heat-processible plastics laminate. The trays were hermetically sealed using a lid film of heat-processible plastics laminate. The tray and contents were then placed in a microwave oven and were heated such that the centre of the pack reached a temperature of 95[deg]C. The pack was then transferred to a steam tunnel and pasteurised. Microbiological examination of the cooked pancake product of this Example was carried out after one month and three months' storage at 37[deg]C. The standard plate count and the mould/yeast counts were less than 10 , and less than 10 respectively. Example 2: Ready-to-eat Waffle product

The ingredients were mixed together as in Example 1 and the prepared batter was used to make round waffles. The Aw of the waffle batter was approximately 0.93 at 25[deg]C and its pH was 5.5. The waffles were cooked on each side on a hotplate. The waffles were then transferred to cans. The cans were hermetically closed and then the packs were pasteurised. The Aw of the cooked product was 0.87 at 25[deg]C and its pH was 5.4. Microbiological examination of the cooked product of this Example was carried out in the same way as for Example 1. The results were substantially the same as for Example 1. Example 3: Onions for frying Sliced onions were treated with humectants and citric acid, the mixture having the following composition:

The sliced onions were contacted with the liquor for two hours and pressed to remove excess liquor. This pre-treated product had a weight of about 55% based on the original weight of raw sliced onion taken. The pressed onion was then dried to give a treated onion product of about 25% by weight based on the original raw weight taken. The treated onion was then mixed thoroughly with glycerol in the following proportions:-

It was then filled into flexible heat-processible plastics pouches. The pouches were partially sealed and the pack was then transferred to a steam tunnel and pasteurised. The sealing was completed immediately after pasteurisation and the product allowed to cool. The water activity of the cooled product was 0.86 at 25[deg]C and it pH was 4.8. Microbiological examination of the pasteurised onion product of this Example was carried out in the same way as for Example 1. The results were substantiallythe same as for Example 1. Example 4: VEGETABLE CAKE FOR FRYING Ingredients:-

The textured vegetable protein was treated by adding one part of mince size granules to three parts of a solution containing 16.0% glycerol by weight and 6% salt by weight and then boiling for 5 minutes. The treated granules were separated from the liquor and drained. The carrots were treated by peeling and dicing to give 6 mm x 6 mm x 6 mm cubes, cooking in fourtimes their own weight of waterto achieve a satisfactory texture, soaking one part of the cooked carrot for 20 minutes at 50[deg]C in two parts of a solution containing 11.8% of glycerol and 3.9% of salt, separating from the soak solution and draining and drying to about 44% of their soaked weight.The onions were treated by peeling and dicing to 6 mm x 6 mm x 3 mm dice, cooking in fourtimes their own weight of waterto achieve a satisfactory texture, soaking one part of the cooked onion for 20 minutes at 50[deg]C in two parts of a solution containing 13.5% of glycerol and 4.3% of salt, separating from the soak solution and draining, and drying to about 46% of their soaked weight.

Example 1.

Example 5 TORTELLINI The vegetable cake was prepared in two stages. Firstly the tomato puree, dried and whole egg, vegetable oil, salt, glycerol and rusk were mixed together thoroughly. Then the treated vegetables were added to this mix. The complete mix was divided into portions and these were moulded into square form cakes. The cakes were placed in heatprocessible plastics pouches. The pouches were partially sealed and preheated in a microwave oven until the centre of the pack reached 90[deg]C. Sealing was completed and the packs were then pasteurised. The water activity of the cooked product was 0.86 at 25.C and its pH was 4.9. Microbiological examination of the pasteurised onion product of this Example was carried out in the same way as for Example 1. The results were substantially the same as for Ingredients: Pasta

Filling

The beef and onions were precooked together with a little added salt. They were then cooled. This blend was then ground, transferred to a mixer and the remainder of the filling ingredients were added. The filling was mixed and then fed to a tortellini former. The semolina flour, citric acid, egg and water were weighed out and mixed. The mass was fed to a sheet extruder and thence to the tortellini former. Tortellini were formed having about 30% by weight offilling and 70% by weight of pasta. The whole tortellini were blanched and then dried to 25% moisture content by weight based on the total pasta and filling together. The whole tortellinis were packed into thermoformed trays formed from a heat-processible plastics laminate. The trays were hermetically sealed using a lid film of heat-processible plastics laminate. The sealed packs were pasteu rised. The product was cooled. The resultant Aw was 0.89 at 25[deg]C and its pH was 5.4. When the two parts of the product-the filling and the pasta-were separated and tested, it was found that equilibration of the water activities had occurred through migration of salt and sodium glutamate from the filling to the pasta during the production process. The pH's of each component were also in equilibrium. A microbiological examination of the product from Example 5 was carried out in the same way as that for Example 1 and the results were substantially the same as for Example 1.

Claims

1. A pasteurised intermediate moisture food product having a water activity of from 0.86 to 0.91 and a pH of from 4.5 to 5.5, said food product having been pasteurised in containers which have been hermetically sealed before, during or immediately after pasteurisation.

2. A food product as claimed in claim 1 wherein the water activity is obtained by drying the food product or at least a part of the ingredients thereof or by incorporating at least one edible humectant into the food product, or by a combination thereof.

3. Afood product as claimed in claim 2 wherein the humectant is selected from water-soluble sugars, salts, polyhydric alcohols and acids, or a mixture thereof.

4. A food product as claimed in claim 3 wherein the humectant is selected from glycerol, sucrose, dextrose, polypropylene glycol, sodium chloride and sorbitol or a mixture thereof. 5. A food product as claimed in any of the preceding claims wherein the pH in the range of 4.5 to

5.5 is achieved by incorporating acetic, citric, lactic, malic ortartaric acid, glucono-8-lactone or sodium acid pyrophosphate, into the food product.

6. A food product as claimed in any of the preceding claims wherein the pasteurisation is effected by heating with steam or hot water, or by microwave heating, or by a combination thereof.

7. A food product as claimed in any of the preceding claims in the form of a pancake, waffle, vegetable, vegetable based product or pasta product.

8. A pasteurised intermediate moisture food product substantially as herein described in any of the Examples.

9. A process for the preparation of pasteurised intermediate moisture food products which comprises pasteurising a food product having a water activity of from 0.86 to 0.91 and a pH of from 4.5 to

5.5 in a container and hermetically sealing the container before, during or immediately after pasteurisation.

10. A process as claimed in claim 9 substantially as herein described.